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2. Mohammad Rezaei Fellowship of Pediatric Pulmonology Respiratory Failure

3. Respiratory distress • Respiratory distress is a clinical impression

4. Respiratory failure • inability of the lungs to provide sufficient oxygen (hypoxic respiratory failure) or remove carbon dioxide (ventilatory failure) to meet metabolic demands.

5. Respiratory failure • Pao2< 60 torr with breathing of room air and • Paco2> 50 torr resulting in acidosis, • the patient's general state, respiratory effort, and potential for impending exhaustion are more important indicators than blood gas values.

6. Respiratory distress can occur in patients without respiratory disease, and • respiratory failure can occur in patients without respiratory distress.

7. Respiratory failure • Acute • Chronic

8. The physiologic basis of respiratory failure determines the clinical picture. • normal respiratory drive are breathless and anxious • decreased central drive are comfortable or even somnolent.

9. The causes: • conditions that affect the respiratory pump • conditions that interfere with the normal function of the lung and airways

10. Respiratory Pump Dysfunction ● Decreased Central Nervous System (CNS) Input • — Head injury • — Ingestion of CNS depressant • — Adverse effect of procedural sedation • — Intracranial bleeding • — Apnea of prematurity ● Peripheral Nerve/Neuromuscular Junction • — Spinal cord injury • — Organophosphate/carbamate poisoning • — Guillian-Barre´ syndrome • — Myasthenia gravis • — Infant botulism ● Muscle Weakness • — Respiratory muscle fatigue due to increased work of breathing • — Myopathies/Muscular dystrophies

11. Airway/Lung Dysfunction ● Central Airway Obstruction • — Croup • — Foreign body • — Anaphylaxis • — Bacterial tracheitis • — Epiglottitis • — Retropharyngeal abscess • — Bulbar muscle weakness/dysfunction ● Peripheral Airways/Parenchymal Lung Disease • — Status asthmaticus • — Bronchiolitis • — Pneumonia • — Acute respiratory distress syndrome • — Pulmonary edema • — Pulmonary contusion • — Cystic fibrosis • — Chronic lung disease (eg, bronchopulmonary dysplasia)

12. Arterial gas composition depends on : • the gas composition of the atmosphere • the effectiveness of alveolar ventilation • pulmonary capillary perfusion • diffusion across the alveolar capillary membrane

13. Alveolar Gas Composition • PAO2 = PIO2 – (PCO2/R) • PIO2 = (BP – PH2O) . Fio2 • PAO2 = [(BP – PH2O) . Fio2] – (PCO2/R)

14. Hypoventilation • VA = VT . RR • low respiratory rate and shallow breathing are both signs of hypoventilation.

15. Dead Space Ventilation • Anatomical • Physiological VD/ VT = (PaCO2-PECO2)/ PaCO2 = 0.33 Increases in decreased pulmonary perfusion: PHTN, hypovolemia, decreased cardiac output

16. Alveolar Ventilation VA = (VT-VD). RR

17. Hypoventilation • The Paco2 increases in proportion to a decrease in ventilation. • Pao2 falls approximately the same amount as the Paco2 increases.

18. Hypoventilation • The relationship between oxygenation and hypoventilation is complicated by the shape of the Hb-dissociation curve • Because of the dissociation curve, a patient who exhibits alarming CO2 retention might have a near normal oxygen saturation.

19. When Paco2 increases from 40 to 70 mm Hg, a dangerous level of hypoventilation, might have a Pao2 that has decreased from 100 to 60 mm Hg and, therefore, maintain an oxygen saturation of 90%. 1. PO2 100 mm Hg= SpO2 of 97% 2. PO2 60mm Hg= SpO2 of90%

20. Thus: oximetry is not a sensitive indicator of the adequacy of ventilation. This is particularly true when a patient is receiving oxygen.

21. Lung/Airway Disease • Diseases of the lung or airways affect gas exchange most often by disrupting the normal matching of V/Q or by causing a shunt. • usually can maintain a normal Paco2 as lung disease worsens simply by breathing more. • hypoxemia is the hallmark of lung disease

22. Ventilation-Perfusion Mismatch

23. hypoxemia due to V/Q mismatch & • hypoxemia due to shunt administering Oxygen

24. Intrapulmonary Shunt

25. Diffusion • diffusion defects manifest as hypoxemia rather than hypercarbia. • Examples : interstitial pneumonia, ARDS, Scleroderma, Pulmonary lymphangiectasia,…

26. Monitoring a Child in Respiratory Distress and Respiratory Failure

27. Clinical Examination • Clinical observation is the most important component of monitoring.

28. ABG & Oximetry • ABG /CBG/ VBG • Oximetry - Oximetry provides an invaluable and usually accurate measurement of oxygenation. - important to recognize its technical limitations

30. Acute Respiratory Failure

31. ARF • most common cause of cardiac arrest in children. When presented with a child who has: • a decreased level of consciousness, • slow/shallow breathing, or increased • respiratory drive, the possibility of ARF should be considered

32. First: • to assure adequate gas exchange and circulation (the ABCs). • Oxygen Administration to maintain …. • If Ventilation is or appears to be inadequate ….. • Intubation ? Need ICU

33. Chronic Respiratory Failure

34. CRF is seen most commonly in children who have: • Respiratory muscle weakness (muscular dystrophy, anterior horn cell disease) or • severe chronic lung diseases (BPD, end-stage cystic fibrosis)

35. usually has an insidious onset • Most children do not have dyspnea. • PH normal or near normal , unless….. • Recognizing need careful monitoring of children at risk for CRF

36. Disordered sleep • Daytime hypersomnolence • Morning headaches • Altered mental status • Increased respiratory symptoms • Cardiomegaly • Decreased baseline oxygenation • CRF often presents first during sleep • Develops an intercurrentillness , Fever